A pulse combustor is a device in which a mixture of air and fuel is initially ignited by, for example, an ignition rod. The ignited gases expand rapidly with an associated rapid increase in pressure and temperature. A resultant pressure wave travels down the device expelling the burnt gases out of an exhaust region. Heat exchange occurs at the walls of the device cooling the gases and enhancing the pressure drop occurring after passage of the pressure wave. This pressure drop due to expansion of the gases combined with the cooling caused by heat exchange at the walls causes the pressure inside the combustion chamber to drop below the ambient pressure (i.e. negative pressure) allowing new gases to be drawn into the combustion chamber. The exhaust flow comes to a rest, with some gases exiting the plates and some returning into the combustion chamber. The flow in the exhaust region reverses and compresses the new air and gas mixture and with the temperature in the combustion chamber still being high, ignition occurs once again. The pulse combustor is used primarily as a hot water boiler, water heater, or low and high pressure steam boiler.
U.S. Pat. No. 4,968,244 describes a pulse combustor with a radial exhaust chamber and a carburetor coupled to the combustion chamber for injecting a pre-determined distribution of fuel mixture into the combustion chamber. The design of the casing of the exhaust chamber comprises an inside plate and outside plate located on each side of the combustion chamber. The exhaust chamber has spiral coolant grooves machined onto in the inside plate which are covered by the outside plate to form a coolant passageway. The usage of two plates bonded together and machining a spiral groove in the plate makes construction difficult and expensive. Moreover, the rapid heating and cooling stresses the bonding between the disc and plate making the device susceptible to coolant leaks. Finally, the somewhat complex design of the carburetor adds to the expense of the device. Also, operation of this design is limited to a high gas pressure which can be above regulated levels, making it unusable for certain areas, such as residential.
PCT Application No. WO97/20171 describes a pulse combustor having a central combustion chamber surrounded by an exhaust chamber, wherein a portion of the combustion and exhaust chambers are formed between two spaced apart walls of spiral wound coolant tubing. The coolant tubing, which forms the walls, provides much greater heat transfer area while at the same time considerably simplifying the construction of the combustor. A fuel nozzle is located at an inlet to the combustion chamber and a spark generator is provided in the combustion chamber and proximate the nozzle in order to ignite the fuel entering the pulse combustor upon startup.
The limitations on the radius of the combustion chamber and the radius of the tail pipe result in a limit to the total amount of power (BTU's of heat generation) achieved by the pulse combustor. Therefore, a combustor is needed that is scaleable to achieve an increased power output.
It is an object of this invention to provide a pulse combustor that has a scaleable power output.
It is a further object of this invention to provide a modified burner for a pulse combustor that provides for a scaleable power output.